Use this command (Data tab > Miscellaneous group) to create and edit individual addons in the standard database (in classic view, select Database menu > Addons). This command opens the Addon window where you can enter information about applying and calculating an addon.
Addons is available only if a standard database is open.
Tip: To edit or create addons from the Totals window, select Edit Addon or Create One-time Addon from the shortcut menu.